Evaluation of a thyroid fluorescent scanning system of concentric source-detector design

A concentric source-detector system for thyroid fluorescent scanning is described, including fundamental parameters of system response and adaptation of a conventional rectilinear scanner for use with it. The basic system consists of twenty 1-Ci sources of 241Am, a 500-mm2 Si(Li) detector, and associated pulse-height electronics. The image-forming equipment of the rectilinear scanner is retained. We have developed a clinical imaging technique that provides a photon density of 600-800 counts/cm2 over the thyroid gland in subjects with normal iodine pools. Comparisons are made between the outrigger design for fluorescent scanning and conventional emission scanning.